Which RTD is less affected by lead wire resistance?
A. Pt10
B. Pt500
C. Pt100
D. Pt1000
View Answer
Answer: D
Explanation:
Pt1000 RTDs are less affected by lead wire resistance because their base resistance is much higher than that of other RTD types.
At 0°C:
- Pt10 = 10 Ω
- Pt100 = 100 Ω
- Pt500 = 500 Ω
- Pt1000 = 1000 Ω
Consider a lead wire resistance of 2 Ω:
For a Pt100
Error percentage:
(2 ÷ 100) × 100 = 2%
For a Pt1000
Error percentage:
(2 ÷ 1000) × 100 = 0.2%
The same lead wire resistance produces a much smaller measurement error in a Pt1000 because the sensor’s resistance is higher.
Why Pt1000 Performs Better
Lower percentage error from cable resistance
Better signal-to-noise ratio
Improved accuracy in 2-wire installations
Suitable for long cable runs
Although 3-wire and 4-wire configurations are commonly used to compensate for lead resistance, among the RTD types listed, Pt1000 is inherently the least affected by lead wire resistance.
Therefore, Option D (Pt1000) is the correct answer.